You will ruin your credit. Your loan will balloon to a huge number, with the increased interest rate you get, plus fees and penalties - I've seen k loans go up to 0k, so this is not something to be trifled with. They will ornamentation your wages - I've seen them take over half a person's paycheck. They will take your wage tax refunds. They can, and will, even take your social protection once you're old.
In addition, if your loan required you to have a co-signer, such as your parents, they'll go after Them. This will ruin their credit, etc.
Students Loans Gov
It is, in other words, very bad news. And student loans can't be discharged via bankruptcy, so you precisely can't get rid of this debt.